Mower cutting deck having a height of cut adjustment system with deck suspension linkages that each have an easily acessible threaded adjuster for deck truing or rake angle setting purposes

ABSTRACT

A mower carrying a rotary cutting deck has a height of cut system for adjusting the vertical position of the deck relative to the mower frame for changing or adjusting the height of cut. The height of cut system comprises a pair of parallel cross shafts that carry a plurality of pivotal suspension linkages that connect to the deck, the cross shafts and linkages pivoting jointly with one another and with a pivotal control lever. One of the cross shafts carries a torsion spring to counterbalance the weight of the deck. The control lever is maintained in a plurality of adjusted pivotal positions by a height selection bracket fixed to the frame with the height selection bracket being capable of having its position changed or adjusted relative to the frame by a single adjustment bolt. Each suspension linkage has its effective length adjusted by turning a threaded adjuster carried at the upper end of a connecting rod that is part of each linkage to allow the deck to be leveled relative to a reference plane. The adjustment of the height selection bracket is accomplished without affecting the length adjustments previously made to any of the suspension linkages.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 12/009,613 filedJan. 8, 2008.

TECHNICAL FIELD

This invention relates to a rotary cutting deck mounted to and carriedon a mower. More particularly, this invention relates to a height of cut(HOC) system that vertically moves the cutting deck up and down relativeto the mower frame, and thus relative to the ground, to adjust theheight of cut of the grass.

BACKGROUND OF THE INVENTION

Riding mowers having a zero radius turn (ZRT) capability are well knownin the mowing art. Such mowers have a frame that carries a power source,such as an internal combustion engine, for propelling the frame over theground and for providing power for mowing. Two powered rear drive wheelsare carried on the frame with the front of the frame having a pair ofunpowered front wheels, the wheels collectively supporting the frame forrolling over the ground. Often, the unpowered front wheels are casterwheels.

The rear drive wheels in a ZRT mower are individually powered byseparate hydraulic drive motors that receive pressurized hydraulic fluidfrom a hydraulic system driven by the power source of the mower. Thedrive motors are individually controlled by separate control leversplaced adjacent an operator's seat provided on the mower frame. Themower is steered by advancing one lever farther than the other to causeone drive motor, and thus the drive wheel on one side of the mower, torotate faster than the other drive motor and drive wheel, therebycausing the vehicle to turn. Very sharp spin or ZRT type turns can beaccomplished by advancing one control lever forwardly while pulling theother control lever rearwardly to cause the drive wheels on the oppositesides of the mower to simultaneously rotate in opposite directions.

A rotary cutting deck is carried at the front of the mower. The cuttingdeck usually houses a plurality of cutting blades that rotate aboutsubstantially vertical axes to cut grass in horizontal cutting planes.The blades are typically staggered relative to one another with a centerblade being offset forwardly of a pair of side blades located on eitherside of the center blade. This allows the orbits of the cutting bladesto overlap without having the blades contact one another, thus avoidingthe need for timing the rotation of the blades. As the mower is drivenover the ground and the blades are rotated, the blades cut a relativelylarge unbroken swath of grass during each pass of the mower. Exmark Mfg.Co., Inc. manufactures and sells ZRT mowers of this type under its LazerZ brand name.

To change the height of cut of the grass, the cutting deck is verticallymoved up and down relative to the mower frame and thus relative to theground to change the height of the cutting blades relative to theground. In many known mowers, the HOC system used to do this includesmultiple suspension links to the cutting deck. These movable links moveup and down simultaneously with one another under the action of a singlecontrol lever. The control lever has a plurality of discrete adjustedpositions relative to the mower frame, often established by the controllever engaging against a pin, to allow the height of cut of the cuttingdeck to be adjusted in a plurality of discrete increments. The height ofcut is adjusted by changing the location of the pin within an array ofadjustment holes provided therefor on the mower frame. The pin isselectively inserted by the operator into whichever adjustment holecorresponds to the desired height of cut.

In HOC systems of this type, it is desirable to be able to level thecutting deck relative to a reference plane, such as a ground plane or arake angle plane. This can be done in prior art mowers by adjusting theeffective distance between the suspension links and the cutting deck.However, in making the cutting deck leveling adjustments, the actualheight of cut might vary from the nominal height of cut provided by thelocation of the pin at the completion of the cutting deck levelingadjustments. Thus, the operator will have to readjust the cutting deckleveling adjustments until the cutting deck is level to the desiredplane at the same time the actual height of cut corresponds to thenominal height of cut. This can be a cumbersome, time consuming andlabor intensive adjustment operation.

Further, the pin/hole type of HOC system provides only a plurality ofdiscrete heights of cut. Infinite heights of cut can be obtained usingthreaded adjusters, but such adjusters require many turns to adjust theheight of cut over a wide range of travel. Thus, it would be desirablein HOC systems to provide a system in which discrete heights of cut canbe easily and quickly selected, such as by inserting a pin within aselected hole, but which would also permit the operator to quickly andeasily obtain heights of cut in between the preset discrete heights ofcut.

The cutting decks used on mowers of this type are often quite large andheavy. Counterbalance springs have been used in prior HOC systems tohelp the operator lift the cutting deck when going from a lower to ahigher height of cut. However, most HOC systems of this type use a pairof tension springs as counterbalance springs. These springs surround apair of longitudinal connecting rods that run over the top of thecutting deck adjacent opposite sides of the mower. Such springs aretypically exposed and in plain view due to the location of theconnecting rods. Thus, to some extent, the springs are prone to beingdamaged and present an obstacle that the operator has to step over ifthe operator were to attempt to mount the mower from either side of thecutting deck.

SUMMARY OF THE INVENTION

One aspect of this invention relates to an improved mower of the typehaving a mower frame. A rotary cutting deck is carried by the frame. Aheight of cut system vertically moves the cutting deck upwardly anddownwardly relative to the frame to adjust the height of cut of thegrass. The height of cut system comprises a plurality of pivotalsuspension linkages connecting the cutting deck to the frame. Theimprovement relates to the pivotal suspension linkages with each linkagecomprising a pivotal link that rotates about a substantially horizontalaxis on the frame. A pivot pin is pivotally carried by the pivotal linkadjacent one end thereof. An elongated connecting rod extends through abore in the pivot pin. A lower end of the connecting rod is pivotallyconnected to the deck and an upper end of the connecting rod extendsabove the pivot pin. At least a portion of the upper end of theconnecting rod is threaded. A threaded adjuster is engaged with thethreaded upper end of the connecting rod and bears against the pivotpin. Rotation of the threaded adjuster on the threaded upper end of theconnecting rod varies the effective length of the connecting rod betweenthe deck and the pivot pin of the link.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be described more completely in the followingDetailed Description, when taken in conjunction with the followingdrawings, in which like reference numerals refer to like elementsthroughout.

FIG. 1 is a perspective view of a mower having the HOC system of thisinvention for adjusting the height of cut provided by the cutting deck;

FIG. 2 is a perspective view of a portion of the frame of the mower andof a portion of the cutting deck, particularly illustrating the HOCsystem according to this invention for adjusting the height of cutprovided by the cutting deck;

FIG. 3 is an enlarged perspective view of a portion of the HOC system ofFIG. 2, particularly illustrating a torsion spring for biasing thecutting deck upwardly relative to the mower frame for transferringweight from the cutting deck to the mower frame;

FIG. 4 is a perspective side view of one end of one cross-shaft of theHOC system of FIG. 2, particularly illustrating the bearing with aninner Delrin sleeve for supporting the end of the cross-shaft;

FIG. 5 is an enlarged perspective view of another portion of the HOCsystem of FIG. 2, particularly illustrating a height selection pin ofthe HOC system installed in one selected height adjustment hole in anarray of height adjustment holes provided in a height selection bracket;

FIG. 6 is a perspective view similar to FIG. 5, particularlyillustrating the height selection pin having been disengaged from any ofthe height adjustments holes in the height selection bracket;

FIG. 7 is a perspective view of the height selection bracket and HOCsystem of FIG. 2 from the opposite side than the side depicted in FIGS.3 and 4;

FIG. 8 is a perspective view similar to FIG. 7, but having thelongitudinal connecting rod and the outside of the height selectionbracket removed to better illustrate the single point adjustment boltfor tilting or pivoting the height selection bracket relative to themower frame;

FIG. 9 is an enlarged perspective view of another portion of the HOCsystem of FIG. 2, particularly illustrating one of the pivotalsuspension linkages that suspend the cutting deck;

FIG. 10 is an enlarged perspective view similar to FIG. 9 of thesuspension linkage, but with portions thereof having been exploded toillustrate the threaded adjuster used to fine tune the height at whichthe cutting deck is suspended by the pivotal link; and

FIG. 11 is a perspective view of the components of the HOC system ofFIG. 2.

DETAILED DESCRIPTION

Referring first to FIG. 1, a mower 3 has a frame 6 that supports arotary cutting deck 4 adjacent the front thereof. Frame 6 is supportedfor rolling over the ground by a pair of rear drive wheels 7 r, only oneof which is shown in FIG. 1, and by a pair of front caster wheels 7 f. Apower source, such as in internal combustion engine 9, is carried at therear of frame 6. An operator's seat 11 is placed forward of engine 9 andgenerally between rear drive wheels 7 r for carrying a seated operator.Two control levers 13 are used by the operator to control the steeringand propulsion provided by rear drive wheels 7 r in a manner well knownfor zero radius turn (ZRT) mowers. Other operational controls areprovided for starting and stopping the operation of deck 4. Mower 3 asillustrated herein is similar to, but is not limited to, the Lazer Zmowers manufactured and sold by Exmark Mfg. Co., Inc., the assignee ofthis invention.

Referring now to FIG. 2, one embodiment of a height of cut (HOC) systemaccording to this invention is generally illustrated as 2. HOC system 2adjusts the vertical height of deck 4 relative to the ground to adjustthe height of cut of the grass being mowed. Only those portions of deck4 and of mower 3 that carry deck 4 that are needed to understand thestructure and operation of HOC system 2 have been shown in FIGS. 2-11.

Referring to FIG. 1, mower frame 6 has a pair of laterally spaced,longitudinally extending side rails 8. Side rails 8 are secured togetherby a plurality of longitudinal and lateral cross members welded thereto.Vertical sleeves or hubs 12 are provided at the front of side rails 8.Hubs 12 rotatably journal the vertical pivot stems of the front casterwheels 7 f. Rear driven wheels 7 r are mounted laterally outboard ofside rails 8 towards the rear ends thereof. Deck 4 is carried beneaththe front portions of side rails 8 as shown in FIGS. 1 and 2.

Referring now to FIGS. 2 and 11, HOC system 2 comprises front and rearcross shafts 16 f and 16 r that are parallel to one another. Both crossshafts 16 are rotatably journalled on mower frame 6 by laterally spacedpairs of bearing blocks 18. Bearing blocks 18 are bolted by bolts 19 toa fixed portion 14 of mower frame 6 adjacent each side rail 8. See FIG.4. Cross shafts 16 will thus rotate about substantially horizontal pivotaxes that extend laterally across and overlie the middle portions of thefront and rear sides of deck 4.

Referring further to FIG. 4, each bearing block 18 is generally U-shapedand is bolted to the underside of the portion 14 of frame 6 to have alow profile. Bearing block 18 is preferably metallic. An inner plasticsleeve 17, made of Delrin, is carried within bearing block 18. Sleeve 17extends around approximately 270° or so, receives one end of a crossshaft 16, and provides a low friction contact surface with cross shaft16. Thus, the combination of a U-shaped bearing block 18 with an innerplastic sleeve 17 effectively journals the end of a cross shaft 16 withboth reduced friction and low profile characteristics, thus constitutingan improvement over simply using a square or rectangular Delrin blockwith a shaft receiving bore as the bearing block. In addition, plasticsleeve 17 does not require the frequent applications of lubricant thatare typically needed for conventional cylindrical metallic bushings.

Each cross shaft 16 terminates in an outer end that is outboard of theadjacent side rail 8. Each end of each cross shaft 16 includes a pivotalsuspension linkage 20 that connects the end of cross shaft 16 to a fixedbracket 22 on deck 4. Thus, deck 4 is suspended or hung beneath crossshafts 16 by the four pivotal suspension linkages 20. Since linkages 20are spread out over deck 4 both laterally and longitudinally, i.e. thereare four linkages 20 arranged in a rectangular pattern relative to deck4, deck 4 is supported in a plane defined by the points where the foursuspension linkages 20 connect to deck 4.

Referring now to FIGS. 9 and 10, each suspension linkage 20 comprises arearwardly extending pivotal link 24 that is fixed to one end of onecross shaft 16 to rotate with cross shaft 16. The other end of link 24is forked having a pair of parallel fork arms 26. A pivot pin 28 ispivotally supported between fork arms 26 with the outer ends of pivotpin 28 being received in a pair of aligned bores 27 in fork arms 26. Thetop central part of pivot pin 28 is cut away to form a flat, upwardlyfacing bearing surface 30 in the middle of pivot pin 28. Pivot pin 28includes a generally vertically extending bore 32 passing from top tobottom through pivot pin 28 with the upper end of bore 32 being locatedin the middle of upwardly facing bearing surface 30 as shown in FIG. 10.

Suspension linkage 20 further includes a generally vertical connectingrod 34 having an eyelet 36 on the lower end thereof. As shown in FIG. 5,a bolt 38 passes through a hole 37 in eyelet 36 and into and throughdeck bracket 22 with the shank of bolt 38 serving as a pivot connectionbetween connecting rod 34 and deck 4. Connecting rod 34 extends upwardlyfrom its pivotal connection to deck 4 through bore 32 in pivot pin 28.Connecting rod 34 is long enough so that its upper end terminates wellabove pivot pin 28. The upper end of connecting rod 34 is threaded asshown at 35 in FIG. 10. Connecting rod 34 and pivot pin 28 are bothsolid metallic members and are not themselves flexible.

The threaded upper end 35 of connecting rod 34 carries a threadedadjuster 40 in the form of a hollow cylinder with a fixed nut 42 carriedon the top thereof. Connecting rod 34 is threadedly engaged with thethreads in adjuster 40, namely with the threads in nut 42. This allowsadjuster 40 to be threaded up and down along the threaded upper end ofconnecting rod 34 to adjust the effective length of connecting rod 34between link 24 and deck 4. This permits precise adjustment of theeffective length of connecting rod 34 for deck leveling purposes as willbe described hereafter. Once a desired position of adjuster 40 isreached, this position can be locked by tightening a jam nut 44 down ontop of adjuster 40.

Pivotal links 24 used in suspension linkages 20 on the right side ofdeck 4 are bell cranks with each of these links 24 also having aforwardly extending link arm 46. See FIG. 7. Links 24 used in suspensionlinkages 20 on the left side of deck 4 do not have such forwardlyextending link arms 46. See FIGS. 2 and 11. Link arms 46 of the rightside suspension linkages 20 are connected together by a longitudinalconnecting rod 48 whose ends are pivotally connected to link arms 46 bypivots 50. Longitudinal connecting rod 48 rotationally links crossshafts 16. Rotation of one cross shaft 16 will rotate the other crossshaft 16 in the same direction and in the same amount by virtue oflongitudinal connecting rod 48. It should also be apparent that thiswill cause all four pivotal links 24 in all four suspension linkages 20to be simultaneously rotated together in the same manner, i.e. in thesame direction and amount as the joint rotation of cross shafts 16.

Referring now to FIG. 8, forwardly extending link arm 46 in the rearsuspension linkage on the right side includes a forwardly protrudingfinger that forms a control lever 52 whose rotational positiondetermines the height of cut provided by HOC system 2. Control lever 52extends into and between a pair of spaced plates 54 that make up aheight selection bracket 56 that is fixed to mower frame 6. As shown inFIG. 6, the innermost plate 54 of height selection bracket 56 is securedby front and rear bolts 58 f and 58 r to an upwardly extending mountingflange 60 on the right side rail of mower frame 6. The outermost plate54 of height selection bracket 56 is carried and supported by theinnermost plate with the two plates 54 being spaced apart by a gap 62.It is this gap 62 into which control lever 52 extends.

Height selection bracket 56 carries an array of height adjustment holes64. A height selection pin 66 can be inserted into any one hole 64 inheight selection bracket 56 to select a different height of cut. FIG. 6shows height selection pin 66 disconnected from any height adjustmenthole 64. FIGS. 3, 5 and 6 show height selection pin 66 inserted into aheight adjustment hole 64 _(max) that provides the maximum height ofcut. Height selection pin 66 simply serves as a stop that coacts againstcontrol lever 52 to set the rotational position of control lever 52. Theweight of deck 4 acting through HOC system 2 will tend to always biascontrol lever 52 into engagement with height selection pin 66.

As shown in FIG. 8, height selection bracket 56 includes a pivotal latch68 for latching control lever 52 in the maximum height of cut position.If the operator wishes to lower the height of cut to something otherthan the maximum height of cut, the operator will reposition heightselection pin 66 into one of the other height of cut adjustment holes64. The operator can then release pivotal latch 68 by pulling back on alatch handle 70. Once HOC system 2 is unlatched, the rest of HOC system2, including cross shafts 16 and the four pivotal links 24, will allrotate in the counter-clockwise direction A in FIG. 8 until controllever 52 contacts height selection pin 66 in its new location. Rotationin the direction A in FIG. 8 causes deck 4 to lower relative to mowerframe 6 and relative to the ground to decrease the height of cut. Theminimum height of cut is provided when height selection pin 66 islocated in height adjustment hole 64 that is highest and farthest to therear in the array of height adjustment holes 64, which hole is indicatedat 64 _(min) in FIG. 8.

The operator can move deck 4 back up from a lower to a higher height ofcut using a foot pedal 72 that is secured to one of the pivotal links24, namely to pivotal link 24 in right front suspension linkage 20 inHOC system 2. Pushing down on foot pedal 72 causes HOC system 2 torotate in direction B in FIG. 8, which is a direction in which deck 4moves upwardly. As this happens, control lever 52 will start to rotateforwardly relative to the array of height adjustment holes 64 in heightselection bracket 56. When the rear edge of control lever 52 becomesadjacent height adjustment hole 64 corresponding to the desired heightof cut, the operator can move height selection pin 66 into thatcorresponding hole. The operator can then release foot pedal 72 and theweight of deck 4 will keep control lever 52 abutted with heightselection pin 66 in its new hole. Alternatively, the operator can raisedeck 4 to its maximum height of cut position before doing anyrepositioning of height selection pin 66.

If deck 4 is returned by the operator to its maximum height of cutposition, pivotal latch 68 will be engaged by control lever 52 as deck 4rises. The bias of a spring 67 had returned pivotal latch 68 to itsusual position in the path of control lever 52 after pivotal latch 68was initially unlatched by the operator pulling rearwardly on handle 70and control lever 52 swung past latch 68 when deck 4 was being lowered.However, with deck 4 now being raised, control lever 52 is able to camor push latch 68 out of the way against the bias of spring 67 as deck 4moves back towards its maximum height of cut position. Once controllever 52 clears latch 68, latch 68 reengages against control lever 52 asshown in FIG. 8 to again hold or lock deck 4 in its maximum height ofcut position. Thus, latch 68 automatically resets into a lockingrelationship with control lever 52 whenever deck 4 is moved back to itsmaximum height of cut position.

There are some instances where it is desirable for latch 68 to bedisabled during operation of HOC system 2. For example, there are timeswhen the operator desirably wants to move deck 4 upwardly and downwardlynumerous times in a short time interval using just foot pedal 72. Inthis situation, having to unlock latch 68 and having latch 68automatically reset becomes a hindrance.

Accordingly, height selection bracket 56 includes a downwardly facing,J-shaped locking slot 69 at the rear end of the channel 71 in whichhandle 70 is received. If the operator now pulls on handle 70sufficiently rearwardly and then downwardly, handle 70 can be moved downinto locking slot 69. In this position, the bias of spring 67 will holdor retain handle 70 in locking slot 69 with latch 68 simply beingpivoted upwardly into a position where latch 68 is held clear of thepath of travel of control lever 52. In this position, latch 68 iseffectively disabled and deck 4 will not be locked into its maximumheight of cut position every time deck 4 approaches that position. Slot69 is a simple and effective way of disabling the operation of latch 68.

To help the operator overcome the weight of deck 4 in raising deck 4using foot pedal 72, a single torsion spring 74 is provided placedconcentrically around front cross shaft 16 f of HOC system 2. As bestshown in FIG. 3, one end of torsion spring 74 bears up against the rearedge of a tab 76 of a collar 78 that is secured to front cross shaft 16f. The other end of torsion spring 74 is restrained or held down by adownwardly facing U-shaped channel 80 that is fixed to one of the siderails of mower frame 6 by a bracket 82. Thus, as torsion spring 74 triesto unwind, the end bearing against the rear edge of tab 76 of collar 78on front cross shaft 16 f rotates cross shaft 16 in the same clockwisedirection B as is achieved when the operator pushes down on foot pedal72, namely in the direction in which deck 4 is raised. This helpscounterbalance the weight of deck 4 and reduces the amount of downforcethe operator has to apply to foot pedal 72 to raise deck 4.

The use of a single torsion spring 74 around one cross shaft 16 of HOCsystem 2 is preferred as it simplifies prior art designs in whichmultiple compression springs were used around various connecting rods.In addition, referring to FIG. 1, both the front and rear cross shafts16 used in HOC system 2 can be conveniently covered by various shields81, escutcheon plates, or portions of the mower floorboard. Preferably,front cross shaft 16 f is covered by a V-shaped foot rest 83. Theoperator can rest his feet atop or against the rear side of foot rest 83while operating the mower. This also hides, covers and protects torsionspring 74 as well as front cross shaft 16 f. This is a further advantageover the exposed and unprotected springs in prior art designs.

Suspension linkages 20 disclosed as part of HOC system 2 of thisinvention permit the operator to easily and precisely level deck 4relative to a flat plane, such as a reference ground plane or a fore andaft rake angle plane. The effective length of each connecting rod 34between pivotal link 24 in each suspension linkage and deck 4 can beprecisely adjusted by the position of adjuster 40 along connecting rod34. If deck 4 needs to be raised at one suspension linkage 20 andlowered at another to level deck 4, this is done by appropriate rotationof adjusters 40 of the involved suspension linkages 20 in oppositedirections. This is easily done simply by loosening jam nut 44 in eachsuspension linkage 20 and then applying a wrench to nut 42 on eachadjuster 40 to thread adjuster 40 either upwardly or downwardly. Whenjust enough movement of adjuster 40 has been accomplished, jam nuts 44can be retightened.

In addition to the individual adjustments that are designed as part ofeach suspension linkage 20, a single point adjustment 84 is furtherprovided for moving the position of height selection bracket 56 relativeto mower frame 6. Single point adjustment 84 is best shown in FIG. 8.Single point adjustment 84 comprises a first, inverted V-shaped bracket86 fixed to height selection bracket 56 and extending between sideplates 54 thereof, a second upright V-shaped bracket 88 fixed to theunderside of the adjacent side rail 8 of mower frame 6, and a threadedadjustment bolt 90 passing through the two V-shaped brackets 86 and 88.The head 92 of bolt 90 and the nut 94 carried on the top end of bolt 90are both accessible to the operator.

In using single point adjustment 84 on height selection bracket 56, theoperator first loosens the bolts 58 f and 58 r that lock heightselection bracket 56 to the mounting flange 60. When both bolts 58 f and58 r are loosened, bracket 56 can move relative to slots 61 f and 61 rin mounting flange 60. Slots 61 f and 61 r are shaped to allow bracket56 to rotate or pivot about the axis of rear cross shaft 16 r. In anyevent, with bracket 56 thus loosened, the operator can grip both thehead 92 of bolt 90 and nut 94 with suitable tools and rotate one or theother to move the two V-shaped brackets 86 and 88 closer towards oneanother or further away from one another. This will rotate the entireheight selection bracket 56 slightly to move height selection pin 66either closer towards or further away from control lever 52, thusproviding a further incremental adjustment of HOC system 2 using justthe single bolt 90 that is part of single point adjustment 84.

Single point adjustment 84 has various uses. If deck 4 has been leveledrelative to a reference ground or rake angle plane by individuallyadjusting the various suspension linkages 20 as need be, it may be thatthe actual height of cut being delivered by deck 4 will vary slightlyfrom the nominal height allegedly being provided by height selection pin66. In other words, height selection pin 66 might be positioned todeliver a 1″ height of cut, but it is possible that the actual height ofcut being delivered will be 0.9″, or 1.1″, or the like. Thus, singlepoint adjustment 84 allows the operator to true up the actual height ofcut with the nominal height of cut by using bolt 90 to adjust theposition of the entire height selection bracket 56 without affecting thedeck leveling relative to the reference plane. Once this truing upprocess is finished, the operator can then lock height selection bracket56 in this position by tightening down all the bolts 58 used to secureheight selection bracket 56 to flange 60 on side rail 8.

Another possible use of single point adjustment 84 is to be able toobtain intermediate heights of cut that are located in between thediscrete heights of cut provided by the various height adjustment holes64 in height selection bracket 56, again without affecting the deckleveling provided by the adjustment of the suspension linkages 20. Forexample, if height adjustment holes 64 in height selection bracket 56provide only ¼″ incremental changes in the height of cut, one could getsmaller incremental changes from a given position, e.g. a ⅛″ change, byusing single point adjustment 84. In other words, the operator wouldplace height selection pin 66 in one of the two holes that are closestto the actual desired height of cut and then appropriately rotate singlepoint adjustment 84 in the correct direction to additionally move pin 66the right amount needed to get the smaller incremental change that wasdesired.

Various modifications of this invention will be apparent to thoseskilled in the art. Thus, the scope of the invention shall be limitedonly by the appended claims.

I claim:
 1. An improved mower of the type having a mower frame, a rotarycutting deck carried by the frame, a height of cut system for verticallymoving the cutting deck upwardly and downwardly relative to the frame toadjust the height of cut of the grass, wherein the height of cut systemcomprises a plurality of pivotal suspension linkages connecting thecutting deck to the frame, wherein the improvement relates to thepivotal suspension linkages with each linkage comprising: a) a pivotallink that rotates about a substantially horizontal axis on the frame; b)a pivot pin pivotally carried by the pivotal link adjacent one endthereof; c) an elongated connecting rod extending through a bore in thepivot pin, wherein a lower end of the connecting rod is pivotallyconnected to the deck and an upper end of the connecting rod extendsabove the pivot pin, and wherein at least a portion of the upper end ofthe connecting rod is threaded; and d) a threaded adjuster engaged withthe threaded upper end of the connecting rod and bearing against thepivot pin, wherein rotation of the threaded adjuster on the threadedupper end of the connecting rod varies the effective length of theconnecting rod between the deck and the pivot pin of the link; wherein atop central portion of the pivot pin is recessed or cut away to form aflat, upwardly facing bearing surface in the pivot pin with an upper endof the bore being located in the upwardly facing bearing surface, andwherein the threaded adjuster comprises a hollow cylinder whose lowerend is received within the recessed or cut away portion of the pivot pinto be in abutting engagement with the upwardly facing bearing surface.2. The mower of claim 1, wherein the one end of the link carrying thepivot pin is forked and comprises a pair of parallel, laterally spacedfork arms, wherein the pivot pin is pivotally journalled in alignedbores in the fork arms, and wherein the connecting rod passes upwardlybetween the fork arms as it passes through the bore in the pivot pinwith the upper end of the connecting rod and the threaded adjuster beingaccessible from above the fork arms.
 3. The mower of claim 1, wherein athreaded nut is fixedly attached to an upper end of the hollow cylindersuch that the threads of the fixed nut comprise the threads of thethreaded adjuster.
 4. The mower of claim 3, wherein the threaded upperend of the connecting rod passes through the hollow cylinder and thefixed nut comprising the threaded adjuster and extends above the fixednut, and further including a jam nut threadedly received onto thethreaded upper end of the connecting rod above the fixed nut for thepurpose of locking the threaded adjuster in an adjusted position bytightening the jam nut down onto the fixed nut.
 5. The mower of claim 1,wherein the pivotal links of the plurality of pivotal suspensionlinkages are mechanically coupled to one another to simultaneously pivottogether as a unit to change the height of cut, and wherein a singlecontrol member is coupled to the mechanically coupled suspensionlinkages such that pivoting of the control member is accompanied bysimultaneous pivoting of the mechanically coupled suspension linkages,the control member being selectively movable by an operator actionduring a height of cut adjustment operation, and wherein the threadedadjusters for each pivotal link of each pivotal suspension linkage areindependently adjusted by the operator to level or true up the cuttingdeck relative to the desired height of cut or to establish a desiredrake angle of inclination relative to the desired height of cut.